" Highlight all instances of word under cursor, when idle.
function! <SID>AutoHighlightToggle()
    let @/ = ''
    if exists('#auto_highlight')
        au! auto_highlight
        augroup! auto_highlight
            setl updatetime=4000
            echo 'Highlight current word: off'
            return 0
        else
            augroup auto_highlight
                au!
                au CursorHold * let @/ = '\V\<'.escape(expand('<cword>'), '\').'\>'
            augroup end
            setl updatetime=500
            echo 'Highlight current word: ON'
            return 1
    endif
endfunction
command! AutoHighlightToggle call <SID>AutoHighlightToggle()
